Role of a serum phospholipase A1in the phosphatidylserine‐induced T cell inhibition

Abstract
We have previously shown that unsaturated phosphatidylserines inhibit mitogen‐induced T cell activation. We now report that the inhibitory action requires a protein present in bovine and human serum. Partial purification and phospholipase assay show that this protein has phospholipase A activity on phosphatidylserine but not phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositol. In short incubations (1–3 h) 2‐acyl lysophosphatidylserine is produced but in longer incubations thecis‐unsaturated fatty acid is also released. Experiments on peripheral blood mononuclear cells indicate that the unsaturated fatty acid becomes the main responsible for the PS‐induced inhibition and that 2‐acyl lysophosphatidylserine enhances the inhibitory effect of fatty acid.

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